Primary pulmonary hypertension and thromboembolic pulmonary hypertension--similarities and differences.

In a retrospective study of 36 patients with primary pulmonary hypertension (PPH) and 16 patients with chronic large vessel thromboembolic pulmonary hypertension (TPH) the diagnostic value of clinical features, chest radiographs, electrocardiographs, radionuclide lung scanning and cardiac catheterization was assessed. PPH patients were younger, had higher prevalence of Raynaud's phenomenon, right axis deviation, right ventricular hypertrophy on electrocardiograph and higher pulmonary artery pressures than TPH patients, but these features were not diagnostic. Although pulmonary angiography is considered by some to be necessary in distinguishing these two conditions, radionuclide lung scanning proved a safe and effective noninvasive method for this purpose.